1. Field of the Invention
This invention relates to communication networks. More specifically, the present invention relates to interworking communication protocols.
2. Description of the Related Art
Virtual private networks (VPNs) have became a solution for extended corporate networks. VPNs are implemented with tunneling protocols. Tunneling protocols are also employed in the wholesale business model of a network provider. Tunneling conceals an Internet Service Provider's (ISP's)customer's network traffic from the network provider servicing the ISP. Protocols for tunneling evolve with changing requirements and technology. Moreover, new tunneling protocols are introduced with improvements over older protocols. Business decisions can lead companies to either select or reject a given protocol.
For example, the most popular tunneling protocol to implement VPNs currently is the Layer 2 Tunneling Protocol (L2TP). In addition, certain Internet Service Providers (ISPs) have made a decision to implement L2TP in their networks. A network provider, such as a telecommunications company (telecom), servicing corporations utilizing VPNs or ISPs selecting L2TP as the tunneling protocol of choice must conform to the selection or not service customers choosing L2TP.
FIG. 1 (Prior Art) illustrates a network provider only servicing an ISP customer with a specific tunneling protocol and not servicing a different ISP selecting a different tunneling protocol. As FIG. 1 illustrates, subscribers 101 access networks through a network provider 103. The network provider 103 can be any telecom or carrier. The network provider typically has numerous network elements such as routers, hubs, switches, subscriber management systems, etc. In FIG. 1, one of the telecom's network elements 105 is illustrated. The network element 105 can terminate the sessions from the subscribers 101 and tunnel the subscriber sessions to an ISP 109. The tunnel 107 between the network provider 103 and the ISP 109 is a tunneling protocol supported at the telcom's network element 105 and the ISP's network element 111. A different ISP 113 employs a different tunneling protocol on its network element 115. The ISP terminates a tunnel 117 from a different network provider which supports the tunneling protocol selected by the ISP 113. The network provider 103 cannot service the ISP 113 as a customer unless it supports the ISPs selected tunneling protocol.
FIG. 2A (Prior Art) illustrates session switching. In FIG. 2A, a network element 201 establishes a tunnel 203 to another network element 205 which is the tunnel endpoint. In this example, the tunnel 203 carries a subscriber session 202. The subscriber session 202 is tunneled again from network element 205 to a network element 209. The tunnel 207 between the network elements 205 and 209 is implemented with the same tunneling protocol as the tunnel between network elements 201 and 205. The network element 209 terminates the subscriber session.
FIG. 2B (Prior Art) illustrates the network element 205 of FIG. 2A switching the subscriber session 202 with the same tunneling protocol. As illustrated by FIG. 2B, the tunnel 201 of FIG. 2A is terminated at the network element 205. The subscriber session 202 first goes through an authorization sequence. A forwarding process 215 processes a first packet or control packet. A tunnel decapsulation routine 217 in the forwarding process 215 decapsulates the control packet from tunnel encapsulation. The decapsulated packet is then processed by a session decapsulation routine 216. The control packet is then processed by a payload decapsulation routine 219. Control information (e.g., subscriber, domain, etc.) from the control packet is passed to a control process 221. The control process 221 determines if the subscriber transmitted over the session 202 is authorized on the network element. For authorized subscribers, the control process 221 directs the forwarding process 215 how to handle traffic from the session 202. After a control packet is received, data packets begin to arrive at the network element. The data packets are L2TP data packets encapsulating data payloads. If the session 202 is to be tunneled out, then the forwarding process 215 no longer passes payloads to the payload decapsulation routine 219. Instead, after the session decapsulation routine 216, payloads from the session 202 are passed to a session encapsulation routine 218 and then to a tunnel encapsulation routine 223. After tunnel encapsulation, the payloads for session 202 are transmitted out another session 204 through the tunnel 207.
A network provider could update their systems to support new tunneling protocols if a network provider would be willing to send people out to the field to update all of their functioning systems. After updating their systems to support the new tunneling protocol, the network provider would have to recertify all of their systems to comply with telecom regulations. Whenever a new tunneling protocol becomes a solution or a valued customer selects an unsupported protocol, the network provider would have to repeat these tasks. Session switching can terminate a session coming over a first tunnel and switch the session to be transmitted out another tunnel, but session switching is limited to the same tunneling protocol.